Ubuntu MATE: Custom time format for clock panel widget

• Run dconf-editor (as your user)
• Go to org / mate / panel / objects / clock / prefs
• Change the key format to custom
• Change the key custom-format to a strftime format string Show archive.org snapshot

A good, space-saving format string for German users is %d.%m. %H:%M. This shows the current date, month, hour and minute (e.g. 24.12. 23:59).